Rotary sabot projectile

ABSTRACT

A sabot having a thermoplastic body and thermosetting reinforced phenolic ring embedded therein which ring retains a projectile in position in the forcing cone of a gun barrel is disclosed. A split ring plastic retainer is used to hold the sabot in place on the tapered rear portion of the projectile. When the projectile is fired, centrifugal force and heat cause the thermoplastic material to expand engaging both the rifling and side walls of the gun bore and thereby imparting a spinning motion to the projectile, while also acting as an obturator to prevent the escape of propellant gases.

Butler tes atent [1 1 [11] 3,7,426 [451 July 10,1973

[ ROTARY SABOT PROJECTILE [75] Inventor: Rex B. Butler, Dahlgren, Va.

[22] Filed: Apr. 17, 1972 [21] Appl. No.: 244,848

[52] US. Cl. 102/94, 89/1 R [51] Int. Cl. F42b 31/00 [58] Field oi Search 102/93, 94, 49.1, 102/49.2; 89/1 R [56] References Cited UNITED STATES PATENTS 2,996,012 8/1961 Butler 102/93 3,216,356 11/1965 Kaufmann, Jr. 102/93 X 3,431,815 3/1969 Kaufmann, Jr. 102/93 X Primary Examiner-Robert F. Stahl Attorney- R. S. Sciascia and Thomas 0. Watson [57] ABSTRACT A sabot having a thermoplastic body and thermosetting reinforced phenolic ring embedded therein which ring retains a projectile in position in the forcing cone of a gun barrel is disclosed. A split ring plastic retainer is used to hold the sabot in place on the tapered rear portion of the projectile. When the projectile is fired, centrifugal force and heat cause the thermoplastic material to expand engaging both the rifling and side walls of the gun bore and thereby imparting a spinning motion to the projectile, while also acting as an obturator to prevent the escape of propellant gases.

10 Claims, 2 Drawing Figures ROTARY SABOT PROJECTILE BACKGROUND OF THE INVENTION This invention relates generally to rotary sabot projectiles and more specifically to those projectiles which are used in rapid fire weapons of the antiaircraft type. These rapid fire weapons generate tremendous heat and are generally fired in a vertical or near vertical position. The guns typically use a separate projectile and casing which contains a powder or propellant to fire the projectile. Loading is accomplished by first placing the projectile into a forcing cone at the rear of the barrel. The sabot on the projectile engages, the riflings which begin adjacent the forcing cone to hold the projectile in position while the casing is loaded below the projectile. Because the guns are near vertical and the fuze on the projectile is activated, it is imperative that the projectile be held in the forcing cone, while the casing is positioned. The interaction of the sabot and n'fling normally serves this function. The metallic sabot used heretofore, however, presents several disadvantages which the instant invention is designed to overcome.

First these metallic sabots are relatively heavy and thus prevent a handling problem. In addition, when the projectile is fired momentum is lost, since some of the energy expended to move the projectile is used to accelerate the heavy metallic sabot. Furthermore, when the projectile clears the barrel and the metallic sabot falls off or breaks apart its pieces which have a high velocity are dangerous to people or adjacent structures on the ground or water.

Thermosetting materials have been employed as a substitute for metal sabots in an effort to solve this problem. These materials are light in weight and disintegrate rapidly upon clearing the gun barrel. However, because they fracture easily they do not function properly as a seal whe moving in the barrel. The result is that propellant gases escape through the fractures in the thermosetting material and tend to force the metal projectile against the rifling lands within the barrel causing excessive wear. Efforts to solve this problem by reinforcing the thermosetting materials have been unsuccessful.

Thermoplastic sabots wer employed in an effort to remedy both of the above problems. However, because of the heat generated in a rapic fire weapon, well above 500F and often above 800F, these sabots could not hold the projectile in the forcing cone while the casing was positioned. The heat causes the thermoplastic material to soften and at times melt. Because the rapid fire weapons are aimed in a vertical or near vertical position the sabot and projectile mere slip from the rifling lands. The instant invention solves all of the above problems.

SUMMARY OF THE INVENTION The instant invention consists of a rotary sabot projectile having a subcaliber core, Le. a core whose caliber is less than that of the gun barrel, having a tapered or a frustro-conical rear position. Circumscribing the rear portion is a thermoplastic obturator ring having a rotating band embedded therein. A split ring thermoplastic retainer is used to hold the obturator ring on the tapered rear portion of the subcaliber core. During loading the rotating band which is composed of a reinforced thermosetting material engages the rifling lands near the forcing cone of the weapon to hold the entire projectile in place while a casing is positioned. Upon firing the softened thermoplastic obturator ring expands forming a seal against the inner wall of the bar rel. The rifling lands impart a spinning motion to the projectile as they engage the obturator ring and rotating band. When the projectile clears the barrel, the centrifugal force causes the split retaining ring to expand and drop off. The obturator ring and rotating band are also free to drop off the rear of the projectile but due to the grooves in both and the centrifugal force imparted on both by the rifling lands both will generally disintegrate into many pieces. The pieces are light in weight and present relatively little danger to those in the adjacent area.

OBJECTS OF THE INVENTION An object of the present invention is the provision of a light weight sabot for projectiles that will disintegrate upon clearing the barrel.

Another object is to provide a rotary sabot projectile for use in rapid fire guns that employs a thermoplastic obturator for sealing and yet is able to maintain itself in the hot forcing cone of a rapid fire weapon.

Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a preferred form of the invention;

FIG. 2 is a longitudinal sectional view illustrating in part the forcing cone and barrel of a rapid fire weapon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1, which illustrates the preferred embodiment of the rotary sabot projectile, shows a subcaliber core 1 having a frusto-conical or tapered rear portion 2. A thermoplastic obturator ring or sleeve composed for example, of nylon circumscribes the rear portion of the subcaliber core 1. The outer diameter of the obturator ring 3 is substantially equivalent to or slightly greater than the caliber of the actual gun barrel. The inner surface of the ring is tapered and frictionally engages the rear tapered portion 2 of the core.

Embedded within the ring 3 is a reinforced thermosetting rotating band 4. The band material may be a fi brous material such as paper or cloth and a thermosetting material selected from the phenolic group of res- Ins.

On the rear of the tapered portion 2 is an annular groove 6. A thermoplastic split retaining ring 5 is inserted in the groove. When the projectile is fired and spin is imparted to the subcaliber core, centrifugal force will cause the ring 5 to expand and drop off. Thus the obturator ring 3, if it is has not disintegrated will drop off the rear end of the shell due to the drag.

The rotating band 4 serves to hold the rotary sabot projectile in the forcing cone 9 as seen in FIG. 2. When the projectile is loaded, the rifling lands 11 which being adjacent the forcing cone 9 cut into the rotating band 4 and in affect cooperate with it to retain the projectile in the forcing cone of the barrel 10, while a casing (not shown) having a propellant therein is loaded below the projectile. The obturator ring 3 which may be slightly larger than the caliber of the gun will not hold it in the forcing cone, since it is made of a thermoplastic material which when heated softens rapidly and would in fact allow the projectile to slip out of the forcing cone.

When the casing is detonated hot propellant gases push against the rear of the projectile and the sabot. The heat and pressure cause the-thermoplastic obturator ring to expand and engage the lands of the rifling and the gun side walls to form a gastight seal. As the projectile moves through the barrel, grooves are made in the rotating band 4 and ring 3. The grooves formed weaken points along the surface of the band and ring which allow them to break up due to the centrifugal force when the projectile leaves the gun. However, if

they do not disintegrate, ring .5 will expand and slip off .5

allowing the drag forces to push the ring and band from the rear of the projectile.

Obviously many modifications and variation of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the apended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A rotary sabot projectile for use in an automatic weapon having a forcing cone therein, comprising a subcaliber core having a forward end and a rear end;

a tapered portion on the rear of said core;

a thermoplastic obturator ring circumscribing said tapered portion;

a rotaing band composed of thermosetting material surrounding and embedded in said ring; and retaining means to hold said ring on said core.

2. The rotary sabot projectile of claim 1 wherein said thermoplastic obturator ring is composed of nylon.

3. The rotary sabot projectile of claim 1 wherein said rotating band is composed of a reinforced phenolic.

4. The rotary sabot projectile of claim 3 wherein said thermoplastic obturator ring is composed of nylon.

5. The rotary sabot projectile of claim 4 wherein said rotating band is composed ofa paper reinforced phenolie.

6. A sabot for use on projectile adapted to be used in a weapon having a forcing cone therein with rifling beginning adjacent said forcing cone comprising:

an annular thermoplastic obturator ring; and

means composed ofa thermosetting material embedded in said ring for cooperating with said rifling and holding said projectile in said forcing cone when said rifling is above 500F.

7. The sabot of claim 6 wherein said means comprises an annular band composed of a reinforced phenolic and said band has an outer diameter greater than the outer diameter of said ring.

8. The sabot of claim 6 wherein said band is composed of a paper reinforced phenolic.

9. The sabot of claim 8 wherein said ring is nylon.

10. A rotary sabot projectile comprising:

a subcaliber core having a forward end and a rear a frusto-conical portion on the rear end of said core;

an annular thermoplastic obturator ring having a cylindrical outer surface and tapered inner surface circumscribing said frustro-conical portion; an annular rotating band composed of a reinforced phenolic embedded in said ring having a larger outer diameter than the outer diameter of said ring;

an annular groove adjacent the rear of said core in said frustro-conical portion; and

a thermoplastic split retainer ring in said groove to retain said ring and rotating band on said frustroconical portion of said core during handling and loading of said projectile. 

1. A rotary sabot projectile for use in an automatic weapon having a forcing cone therein, comprising a subcaliber core having a forward end and a rear end; a tapered portion on the rear of said core; a thermoplastic obturator ring circumscribing said tapered portion; a rotaing band composed of thermosetting material surrounding and embedded in said ring; and retaining means to hold said ring on said core.
 2. The rotary sabot projectile of claim 1 wherein said thermoplastic obturator ring is composed of nylon.
 3. The rotary sabot projectile of claim 1 wherein said rotating band is composed of a reinforced phenolic.
 4. The rotary sabot projectile of claim 3 wherein said thermoplastic obturator ring is composed of nylon.
 5. The rotary sabot projectile of claim 4 wherein said rotating band is composed of a paper reinforced phenolic.
 6. A sabot for use on projectile adapted to be used in a weapon having a forcing cone therein with rifling beginning adjacent said forcing cone comprising: an annular thermoplastic obturator ring; and means composed of a thermosetting material embedded in said ring for cooperating with said rifling and holding said projectile in said forcing cone when said rifling is above 500*F.
 7. The sabot of claim 6 wherein said means comprises an annular band composed of a reinforced phenolic and said band has an outer diameter greater than the outer diameter of said ring.
 8. The sabot of claim 6 wherein said band is composed of a paper reinforced phenolic.
 9. The sabot of claim 8 wherein said ring is nylon.
 10. A rotary sabot projectile comprising: a subcaliber core having a forward end and a rear end; a frusto-conical portion on the rear end of said core; an annular thermoplastic obturator ring having a cylindrical outer surface and tapered inner surface circumscribing said frustro-conical portion; an annular rotating band composed of a reinforced phenolic embedded in said ring having a larger outer diameter than the outer diameter of said ring; an annular groove adjacent the rear of said core in said frustro-conical portion; and a thermoplastic split retainer ring in said groove to retain said ring and rotating band on said frustro-conical portion of said core during handling and loading of said projectile. 